Magnetically controlled reversible friction drive



Oct. 10, 1950 v 515 595]: 2,525,443 MAGNETICALLY'CONTROLLED REVERSIBLE FRICTION DRIVE Filed Dec. :1, 1947 2 Sheets-Shea! 1 PERMANENT MAGNETIC DISKS Tfl s 5 v 6 MOTOR umomccr SHAFT man/el 7"- l lo a N s 4 E g sorrmou DISK CONTROL COIL ,5 PoTENTML '6 FLEXIBLE COUPLING BL CO E PERHEA E R 5 l3 PERMEABLE CORE 80/7 IRON DI Inventor-2 aw His Attorney- Get. 10, 1950 BISCHQFF 2,525,443 I MGNETIQALLY CQNTRQLLED REVERSIBLE FRICTION DRIVE Filed Dec. 31, 1947 2 Sheets-Sheet POTENTIAL 2 SOURCE.

CONTROL cuRR- ENT SOURCE so 'r mow olsk /-SOFT mou DISK COIL 5 4 6 MOTOR UNIDIRECT SHAFT IONAL a MOTOR s -PERMANENT a9 MAGNETIC 30% I I DISK PERHEABLE C RE""" i PERHEABLE CORE TUNING COIL TUNIPQIG COIL: 5 I5 Ihventor: Alfred F.Bisc hof1,

His Attorney.

Patented Oct. 10, 1950 MAGNETICALLY CONTROLLED REVERSIBLE FRICTION DRIVE Alfred F. Bischoff, Ballston Spa, N. Y., assignor to General Electric Company, a corporation of New York Application December 31, 1947, Serial No. 794,924

9 Claims.

This invention relates to reversible drive mechanisms and more particularly to such mechanisms as are used in automatic tuning arrangements for radio receivers and the like.

It is an object of this invention to provide a reversible drive mechanism that is inexpensive and simple to construct and in which a simple unidirectional non-reversible driving motor is utilized.

A further object of this invention is to provide a reversible drive mechanism that may be operated from a low potential unidirectional power source and which consumes a relatively small amount of energy.

Another object of this invention is to provide a reversible drive mechanism that is instantly reversible, and in which the control thereof requires a relatively small amount of energy.

Yet another object of this invention is to provide such a mechanism having a low inertia, thus assuring that the drive motion is arrested at a desired point and precluding the fly-wheel effect by which such mechanisms having a tendency due to their inertia to overrun the desired point.

The features of this invention which are believed to be new are set forth with particularity in the appended claims. The invention itself, however, together with further objects and advantages thereof may best be understood by reference to the accompanying drawings wherein Fig. 1 shows one form of a reversible drive mechanism embodying the present invention. Fig. 1A shows a side view of the permanent magnet discs included in the mechanism of Fig. 1. Fig. 2

shows a preferred modification of the reversible drive mechanism. Fig. 3 shows a section of a control circuit which may be used for controlling the operation of the reversible drive mechanisms. Figs. 4 and 5 are modifications of the mechanism of Fig. 2.

Referring now to the drawings, Fig. 1 shows one embodiment of the invention wherein the mechanism drives the tuning system of a radio receiver. It is to be clearly understood, however, that this application of the reversible drive mechanism is given by way of example only, as the mechanism may be applied to any system which requires a reversible drive that may be easily controlled and brought quickly to a stop at any desired position.

A unidirectional motor is designated by the rectangle l, and operating potential is applied thereto from a suitable energizing source by way of terminals 2. The motor 2 is supported on a base 3 and imparts to shaft 4 a unidirectional rotation, shaft 4 being supported by bearings 5 and 6, as shown. A pair of permanent magnetic discs I and 8 are keyed to the shaft 4. Disc 1 may be magnetized so that its periphery exhibits a north pole and disc 8 may be magnetized so that a south pole appears at its periphery, as clearly shown in Fig. 1A. It is necessary that these discs be magnetized so that their respective peripheral magnetism is of opposite polarity, although it is immaterial which disc has a north pole on its periphery and which has a south pole.

A disc 9 of soft iron, or material with similar magnetic properties, is positioned between the magnetic discs 1 and. 8, disc 9 being keyed to a shaft 10, thereby driving this shaft. The shaft I0 has, in this example, a threaded end I l carrying thereon a rider l2, thus imparting reversible longitudinal motion to the permeable cores H1 in the tuning coils [4. A flexible coupling I5 is included in shaft I0 to allow disc 9 a small amount of lateral freedom. Supporting member [6 serves as a guide for shaft H). A control coil I! surrounds shaft I0 and control potentialis applied thereto by way of terminals 18.

Potential may be applied to motor I by way of terminals 2, thus unidirectionally rotating shaft 5. When the soft iron disc 9 is not magnetized it has a position between the magnet discs I and 8 and no motion is imparted thereto and shaft Ill remains at rest. However, when a unidirectional current is passed through coils I! which surround shaft ID, the soft iron disc becomes magnetized acting either as a north or south pole depending upon the direction of the flow of this unidirectional current through the coil. When the soft iron disc 9 is made to have a peripheral north pole, it will be attracted towards the permanent magnet disc 8 which exhibits a south pole at its periphery and repelled by permanent magnet disc 1 which has a peripheral north pole. The soft iron disc 9 therefore co-acts with disc 8 and by a frictional drive, disc 8 rotates disc 9, and shaft IQ is therefore rotated in one direction. It has been found that the friction between the discs is enhanced by the magnetic state of these discs. When the control current through coils I! is reversed disc 9 immediately co-acts with disc 1, and the rotation of disc 9 and hence shaft I0 is accordingly reversed.

It is, therefore, apparent that when a control potential having a certain polarity is impressed across terminals 18, the shaft Ill rotates in a certain direction, thus imparting a certain longitudinal motion to cores l3. When the control po- 3 tential is discontinued the rotation of the shaft l and motion of cores l3 immediately stops, and when the polarity of the control potential is reversed, the rotation of shaft l8 and the movement of cores i3 is also reversed.

A preferred modification of the above described reversible drive mechanism is shown in Fig. 2, and reference is now made to this figure. The embodiment shown in Fig. 2 is in many respects similar to that shown in Fig. i and like components thereof are designated by like numerals.

As before, unidirectional motor i when energized by potential impressed across terminals 2 rotates shaft 4 in a certain direction. A pair of soft iron discs I?! and 20, similar in appearance to discs 1 and 8 of Fig. l, are keyed to shaft 4 and rotated thereby. Shaft 4. passes through a pair of control coils 2| and 22 which are energized by a control source 23. The control potential provided by source 23 is impressed across the coils 2| and 22 by way of leads 24, 25 and 26. The control circuit is so arranged that when the control potentials across leads 24-25 and 28-25 are balanced, the resultant magnetic field of coils 2|, 22 is zero and the soft iron discs E9 and 20 are therefore demagnetized. When there is an unbalance in potential between the leads 24-25 and 28-25, this gives rise to a resultant magnetic field in coils 2| and 22, and the direction of this resultant field is dependent upon whether the potential between leads 24-25 or 26-25 predominates. The soft iron discs l9 and 28 become magnetized with opposite periph eral polarity of these discs being dependent upon the direction of the resultant field of coils 2%,

A further soft iron disk 2? is keyed by means of a swivel joint to a shaft H1 and drives this shaft. The solid lines show disk 21 in one position and the dotted lines show this disk in an alternative position. Shaft l8 passes through a permanent magnetic disk 28, this disk being rigidly mounted to a support 30 by members 29, and the shaft It being free to rotate in the disc 28 and support 38. The disc 28 is similar in appearance to discs 1 and 8 of Fig. 1 and is magnetized in such a manner that one fac exhibits a north pole and the opposite face a south pole. In the embodiment shown, the surface of disc 28 facing the soft iron disc 2'! is shown, by way of example, to be a north pole.

When the current flow in coils 2| and 22 is balanced, the resultant magnetic field of these coils is zero, and discs l9 and 20 are demagnetized. When discs l9 and 28 are in their demagnetized state the soft iron disc 21 is held in a position normal to shaft ID by permanent magnet 28. When the current flow in coils 2| and 22 is unbalanced, a resultant magnetic field is set up and either disc l9 or disc 28 exhibits a peripheral north pole, depending on the direction of this resultant magnetic field. In the present embodiment it is assumed that disc I8 has a north pole at its periphery. Permanent magnet disc 28, placed in close proximity to soft iron disc 21 induces a. north pole in the surface of disc 27 presented to the periphery of discs 9 and 2B. This causes disc 2! to be attracted to disc 28 and repelled by disc l9. Disc 21 moves on its swivel joint and coacts with disc 20, and by means of frictional drive, disc 21 is rotated in a certain direction, which in turn rotates shaft l8. When there is a control current unbalance in the opposite sense, an opposite resultant field is set up and disc 21 is attracted to disc l9 and repelled by disc 26, and the shaft H] is therefore rotated in the opposite direction. Whenever the control currents through coils 2| and 22 are balanced, disc 27 is held normal to shaft it by permanent magnet disc 28 and hence the rotation of shaft l8 ceases.

Further modifications may be made in this system, for example in the arrangement shown in Fig. 4 the soft iron disc 2'! is replaced by the permanent magnet disc 28. However, this has the disadvantage that the weight of the disc 28 increases the inertia of the system and in addition there would be a tendency in 'such systems for a bond to exist between discs l9 and 20 and permanent magnet disc 28. 4

In a further modification shown'in Fig. 5 the soft iron disc 21 normally bears equally'on discs I9 and 20, and hence when discs l9 and '20 are 'not magnetized disc 27 remains stationary. However, magnetism established by a control current unbalance in coils 2| and 22 causes the force of friction between either disc 2'! andd'isc H! or disc 2'? and disc 28 to increase or decreasedepending on the sense of the control current, thus causing disc 2? and, hence, shaft ID to rotate in a desired direction. This system has the advantage that the direction of rotation of shaft I!) may be reversed by means of a relatively small amount of control energy. p

Referring now to Fig. 3 which-shows a portion of a control circuit for the reversible drive mechanism, and wherein alternating current is utilized quickly to return the system to its normal state when the currents in coils 2| and 22 of Fig. 2 become balanced. The present circuit comprises a pair of electron discharge devices 3| and 32, shown in this instance to be pentode s, although other known types of electron discharge devices may be used. Control potential is'appli ed to terminals 33 and thence to the control electrode 34 and 35 of the respective devices. The cathodes of devices 3| and 32 are connected together and to ground through a resistor 36.' The suppressor electrodes 3'! and 38 are connected tothe common cathode circuit, and the screen electrodes 38 and 48 are connected together, and by way of lead '25, to the common connection of coils Hand 22, which are the control coils of Fig.2. The anodes tl and 42 are connected respectively to coils 2| and 22 as shown by way of resistors 43 and 44 and leads 24 and 25 respectively. The lead 25 is also connected to a source of unidirectional potential B+, thus supplying potential to the anodes and screen electrodes of 'discharge devices 31 and 32.

It is apparent that when a control potential is applied to terminals 33, the sense and amount of unbalance in devices 3! and -32 is dependent on the polarity and amplitude of 'this control potential. The resultant current th reiigh coils 2| and 22 and the operation of the mechanism of Fig. 2 is similarly dependent on the characteristicsof the potential of terminals'33;

It is found in the previousdescribed drive mechanism that there is a tendency forth e soft iron disc to remain in contact with the driving discs after the magnetic field is removed. To

overcome this adhesion, an alternating current may be applied to one of the control coils 2| or 2'2, thus creating an alternating flux of sufiicient strength to release the soft iron disc and yet not sufiiciently high to be detrimental to the operation of the mechanism. This is shown in Fig. 3, wherein alternating current is impressed across terminals 45, and applied to coil 2 l, for example, through a step-down transformer 46 and by way of a direct current blocking capacitor 41. It has been found that most favorable results may be obtained when the alternating current potential has a peak value which is slightly below the unidirectional potential value.

A reversible drive mechanism has therefore been provided, driven by a unidirectional continually running motor, this mechanism being relatively inexpensive and simple to construct, in which the need for complicated reversing switching arrangements is precluded, and which has a low inertia and a minimum fly-wheel effect.

While certain specific embodiments have been shown and described, it will of course be understood that various modifications may be made without departing from the invention. The appended claims are, therefore, intended to cover any such modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a reversible drive mechanism, a shaft member, means for imparting unidirectional rotation to said shaft member, a pair of permanently magnetized discs carried on said shaft member and rotated thereby, 'a magnetizable driven member mounted adjacent to said discs, means for magnetizing said member with either of two polarities, in response to a control current of corresponding polarity, thereby to cause said driven member to be attracted to one or the other of said discs in accord with the polarity of its magnetization, a further shaft member coupled to said driven member, and means to reverse the direction of rotation of said further shaft member in response to changes in the attraction of said driven member from one of said discs to the other.

2. In a reversible drive mechanism, a shaft member, means for imparting unidirectional rotation to said shaft member, a pair of driving members carried on said shaft member and rotated thereby, a driven member mounted adjacent to said driving members, the axis of said driven member being normal to the axis of said driving members, means for magnetizing said members in response to a control current, permanent magnet means for causing said driven member to coact alternately with one or the other of said driving members dependent upon the sense of said control current, a further shaft member coupled to said driven member, the direction of rotation of said further shaft member being reversed as said driven member changes its coaction from one driving member to the other.

3. In a reversible drive mechanism, a shaft member, means for imparting unidirectional rotation to said member, a pair of disc-like driving members mounted on said shaft member and rotated thereby, a disc-like driven member mounted with the axis thereof normal to the axis of said driving members, means for magnetizing said members in response to a control current, permanent magnet means for causing said driven member to coact alternately with one or the other of saiddriving' members dependent upon the sense of said control current, a further shaft member coupled to said driven member, the direction of rotation of said further member being dependent upon the coaction of said driven member with one or the other of said driving members.

4. In combination, a shaft, means for imparting unidirectional rotation to said shaft, a pair of disc-like driving members mounted on said shaft and rotated thereby, a further disc-like member mounted normal to said driving members and a further shaft coupled to said further disc-like member for rotation thereby, magnetic means for magnetizing said members in response to a control current the magnetic polarity of said members being dependent on the sense of said control current, and means responsive to said control current in a certain sense to cause coaction between said further disc like member and one of said driving members for imparting rotation to said further shaft in a certain direction, said last means being responsive to said control current in an opposite sense to cause coaction between said further disc-like member and the other of said driving members for imparting rotation to said further shaft in the opposite direction, and said last means in the absence of said control current preventing coaction between said further disc-like member and said driving members thus arresting the motion of said further shaft.

5. In a reversible drive mechanism, a shaft member, means for imparting unidirectional rotation to said shaft member, a pair of disc-like permanent magnet driving members mounted on said shaft member, a disc-like magnetic driven member of low magnetic retentivity mounted normal to said driving members and positioned intermediate thereto, a. further shaft member coupled to said driven member and rotated thereby, a flexible coupling in said further shaft member for allowing lateral movement of said driven member, means for magnetizing said driven member in response to a control current, permanent magnet means responsive to the magnetization of said driven member for causing coaction between said driven member and one or the other of said driving members dependent on the sense of said control current, the direction of rotation of said further shaft member being dependent upon the coaction of said driven member with one or the other of said driving members.

6. In a reversible drive mechanism, a shaft member, means for imparting unidirectional rotation to said shaft member, a pair of disc-like magnetic driving members of low magnetic retentivity mounted on said shaft member and r0- tated thereby, a magnetic disc-like driven member of low magnetic retentivity mounted normal to said driving members, a further shaft member adapted to be rotated by said driven member, swivel means coupling said driven member to said further shaft member, a permanent magnet disc member mounted adjacent the face of said driven member remote from said driving members, means responsive to a control current for magnetizing said driving members with opposite polarity, said driven member coacting with the periphery of one or the other of said driving members dependent upon the sense of said control current, the direction of rotation of said further shaft member being dependent upon the coaction of said driven member with said respective driving members.

'7. In a reversible drive mechanism, a shaft member, means for imparting unidirectional ro-.

tation to said shaft member, a pair of driving members carried on said shaft member and rotated thereby, a driven member mounted adjacent to said driving members, means for magnetizing said members in response to a control current to cause said driven member to coact alternately with one or the other of said driving members dependent upon the sense of said control current, means including an alternating magnetic field for demagnetizing said members in the absence of said control current, a further shaft member coupled to said driven member, the direction of rotation of said further shaft member being reversed as said driven member changes its coaction from one driving member to the other.

8. In a reversible drive mechanism, a shaft member, means for imparting unidirectional rotation to said shaft member, a pair of disc-like magnetic driving members of low magnetic retentivity mounted on said shaft member and rotated thereby, a magnetic disc-like driven member of low magnetic retentivity mounted normal to said driving members, the periphery of said driven member coacting with the peripheries of said driving members, a further shaft member adapted to be rotated by said driven member, a permanent magnet disc member mounted adjacent the face of said driven member remote from said driving members, means responsive to a control current for magnetizing said driving members with opposite polarity for causing the friction to increase between said driven member and one of said driving members and to decrease be- 8 tween said driven member and the other of said driving members, the direction of rotation of said further shaft member being thereby dependent upon the sense of said control current.

9. In combination, a shaft member, means for imparting unidirectional rotation to said shaft member, a driving member carried on said shaft member and rotated thereby, a driven member mounted adjacent said driving member, means for magnetizing said members in response to a control current, permanent magnet means for causing said driven member to coast with said driving member in response to the magnetization of said members, a further shaft member coupled to said driven member, said further shaft member being rotated when said driven member coacts with said driving member in the presence of said control current, and said further shaft member being stationary in the absence of said control current.

ALFRED F. BISCHOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,038,131 Hemming Sept. 10, 1912 1,296,850 Rainey Mai. 11, 1919 1,368,587 Villiers Feb. 15, 1921 1,960,103 Fierce May 22, 1934 2,167,641 Dewan Aug. 1, 1939 2,178,641 Neumann Nov. 7, 1939 

